1. Field of the Invention
The invention relates to an electromagnetically driven valve device provided as an engine valve of an internal combustion engine for opening and closing a valve element of the valve device by electromagnetic force.
2. Description of the Related Art
An electromagnetically driven valve device of the aforementioned type is described in, for example, Japanese Patent Application Laid-Open Publication No. 2001-126922. This valve device includes an armature that reciprocates together with an engine valve of an internal combustion engine, and electromagnets disposed in the directions of the ends of displacement of the armature. The armature is driven by the electromagnetic attraction force generated between the armature and the electromagnets, thereby opening and closing the engine valve.
In this type of electromagnetically driven valve device, the armature and the electromagnets are normally positioned by retaining them to a housing, as described in Japanese Patent Application Laid-Open Publication No. 2001-126919. The armature is held so as to be slidable in a space between the two electromagnets, and is driven in accordance with the pattern of electrification of the coils of the electromagnets.
As for the housing, an iron or the like is used as a material because of the ease of working at the time of fixation of the electromagnets by welding or the like. However, if such a metal as iron or the like that allows welding is used, a weight increase of the entire device may become a problem. Therefore, if a weight reduction of the device is demanded, a light-weight metal, such as aluminum or the like, is often used as a material of the housing. However, the use of a light-weight metal, such as aluminum or the like, makes it difficult to attach electromagnets to the housing by welding or the like, while achieving a weight reduction of the device. As a result, the electromagnets are indirectly secured to the light-weight metal housing through the use of screws, bolts or the like, thus degrading the ease of assembly.
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